If getting a good to-do list is on your personal to-do list, give the aptly named Tasks a try. Tasks syncs with your Google Tasks account (a little-known service that's integrated into Gmail) and gives you an intuitive interface for managing multiple lists with multiple layers.
The Tasks lock screen widget is clean, simple and easy to use -- and if you have more than one list configured, it can display whichever list you'd like. You can also control how it sorts items and what color scheme it uses.
Tasks is available in both a free ad-supported version and a 99-cent "pro" version.